Hey Guys,

It has been a while since I have been on here but I was hoping someone out there would be able to help me.

I have taken my 02 F150 to 3 different garages but still having no luck.

My check engine light keeps coming on with 2 error codes:
I have taken the following steps below to try and get this fixed because it always happens if the temperature outside is about 70 degrees Fahrenheit or less. Now that winter is on its way, I know I am going to get a lot of trouble with this.

The engine will go up and down between as low as 300rpm and 800rpm when in idle and this will sometimes cause the engine to cut out.

Cleaned mass airflow sensor
Replaced mass airflow sensor
Replaced all spark plugs
Cleaned air filter
Replaced air filter
Checked for vaccum leaks after MAF sensor up to throttle body
Replaced valve cover gaskets

Any help would be greatly appreciated. I am dreading the coming cold months

Winter is coming...

 

Did you check the COMPLETE PCV system from end to end? By far, the most common issue.

 

The PCV elbow behind the intake loves to rot out. All those parts you replaced was a shotgun job, that's not proper diagnosis and troubleshooting.

 

yes check out the PCV valve and hoses/elbows
could also be the intake manifold gasket/cracked

also find better shops, if they can't find a vacuum leak I wouldn't go back

 

Does this model have the IAC?

 

Hey guys,

Thanks for the responses. I do appreciate them.

I completely forgot about the PCV elbow. That was replaced and was one of the first things to be replaced as it had split.

Just so you guys know, the 3rd time I had taken it somehwere was Ford themselves. They wanted $1600 to replace valve cover gaskets (which I had done elsewhere) and still getting the same issue.

I am not sure about the IAC> I will look in to that though!

 

Yes, a 2002 will still have an IAC valve. It's not your problem, it's simply trying to compensate for the real problem.

Your symptoms are still of a vacuum leak. I'd like to know how valve cover gaskets can cause that!

Set your scan tool up to monitor either both of the short term fuel trims or both upstream O2 sensor voltages simultaneously. Run the engine at an idle long enough for the PCM to switch to closed loop operation, then carefully spray brake cleaner or similar around the various parts of the intake while watching the scanner. When the flammable gets sucked into the intake, you'll see a very noticeable spike in the trims (or voltages). You'll be able to zero in on the intake leak very quickly by doing this provided that the problem remains present during testing.

 

I
I believe @projectSHO89 is 'dead on target' on both cause and how to find it quickly. I would like to add a great suggestion that I think was posted by @glc one time. An "un-lit" propane torch will produce the same result as spraying a flammable liquid (and be less messy / less detrimental to rubber parts / or as much a fire hazard).


Also @projectSHO89 - Doesn't the crankcase ventilation system (on that '02) derive its air source from 'metered air'? It does on my '04, and thus - couldn't an air leak in a valve cover gasket, or timing cover, or oil pan gasket for that matter, result in too much air (as determined by the Mass Air sensor) for a proper mixture and lead to P0171/174? To the PCM it seems it would appear the same as any other vacuum leak that affects Both Banks.

 

I suspect a valve cover leak would also leave an oil trail. If the hose with restriction (or PCV) is in place it shouldn't matter if the valve cover is leaking I think.

 

Depends on if it's working properly or not.

DTC pair can also be caused by a bad PCV valve, suggest replacing with Motorcraft only.

 

Awe hell, really?

 

I agree some oil should be visible, but if its in a location that isn't particularly bathed in oil - maybe not. I didn't (don't) know about the '02, but on the '04 5.4L there is no 'positive pressure' or PCV valve by design feature. The crankcase is subjected to intake manifold vacuum all the time, minus a small amount of 'metered air' sourced from the passenger side of the TB, downstream of the air filter. The entire crankcase / vc's are sealed. When I remove my oil filler cap - I can observe the short term fuel trims go positive on my scanner.


I think one of the reasons the engineers did that might be to make it less susceptible to small oil leaks.

 

Smoke test around your intake manifold. My 01 Expedition was throwing the same codes, we repaired, replaced and cleaned everything possible, with no luck. Finally resmoke checked it and found a cracked intake manifold. Replaced with a Dorman unit and no more issue.

 

Thanks everyone for your suggestions. I will be giving all of these a try.

My problem is I work full time, study full time and have 3 little girls so spare time isn't a luxury.

Is there anyway I can perform a smoke test at home or will I have to take it to a garage?

I am going to replace the o-rings this weekend.

 

For a true smoke you would need to go to a dealer or mechanic. The equipment is rather pricey. Some old timers use carb cleaner,but this can be hazardous. Others reccomend starting fluid. Agin can be dangerous. Definitely look at area round intake mounting bolts and water neck.

http://www.popularmechanics.com/cars...a-vacuum-leak/